/* gzio.c -- IO on .gz files
 * Copyright (C) 1995-2002 Jean-loup Gailly.
 * For conditions of distribution and use, see copyright notice in zlib.h
 *
 * Compile this file with -DNO_DEFLATE to avoid the compression code.
 */

/* memgzio.c - IO on .gz files in memory
 * Adapted from original gzio.c from zlib library by Forgotten
 */

/* @(#) $Id: memgzio.c,v 1.5 2006/06/06 21:04:20 spacy51 Exp $ */

#include <stdio.h>
#include <stdarg.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>

#include "memgzio.h"

#ifndef local
#define local static
#endif

#ifndef DEF_MEM_LEVEL
#  define DEF_MEM_LEVEL 8
#endif

#ifndef OS_CODE
#define OS_CODE 3
#endif

#ifndef zmemcpy
#define zmemcpy memcpy
#endif

/*struct internal_state {int dummy;};*/ /* for buggy compilers */

#ifndef Z_BUFSIZE
#  ifdef MAXSEG_64K
#    define Z_BUFSIZE 4096 /* minimize memory usage for 16-bit DOS */
#  else
#    define Z_BUFSIZE 16384
#  endif
#endif
#ifndef Z_PRINTF_BUFSIZE
#  define Z_PRINTF_BUFSIZE 4096
#endif

#define ALLOC(size) malloc(size)
#define TRYFREE(p) \
	{if (p)                            \
		 free(p);}

static int gz_magic[2] = {0x1f, 0x8b}; /* gzip magic header */

/* gzip flag byte */
#define ASCII_FLAG   0x01 /* bit 0 set: file probably ascii text */
#define HEAD_CRC     0x02 /* bit 1 set: header CRC present */
#define EXTRA_FIELD  0x04 /* bit 2 set: extra field present */
#define ORIG_NAME    0x08 /* bit 3 set: original file name present */
#define COMMENT      0x10 /* bit 4 set: file comment present */
#define RESERVED     0xE0 /* bits 5..7: reserved */

typedef struct _MemFile
{
	char *memory;
	char *next;
	int   available;
	int   error;
	char  mode;
} MEMFILE;

typedef struct mem_stream
{
	z_stream stream;
	int      z_err;   /* error code for last stream operation */
	int      z_eof;   /* set if end of input file */
	MEMFILE *file;    /* memoru file */
	Byte *   inbuf;   /* input buffer */
	Byte *   outbuf;  /* output buffer */
	uLong    crc;     /* crc32 of uncompressed data */
	char *   msg;     /* error message */
	int      transparent; /* 1 if input file is not a .gz file */
	char     mode;    /* 'w' or 'r' */
	long     startpos; /* start of compressed data in file (header skipped) */
} mem_stream;

local gzFile gz_open      OF((char *memory, const int available, const char *mode));
local int do_flush        OF((gzFile file, int flush));
local int get_byte     OF((mem_stream *s));
local void check_header OF((mem_stream *s));
local int destroy      OF((mem_stream *s));
local void putLong      OF((MEMFILE *file, uLong x));
local uLong getLong      OF((mem_stream *s));

local MEMFILE *memOpen(char *memory, int available, char mode)
{
	MEMFILE *f;

	if (available <= 8)
		return NULL;

	if (mode != 'w' && mode != 'r')
		return NULL;

	f = (MEMFILE *)malloc(sizeof(MEMFILE));

	f->memory = memory;
	f->mode   = mode;
	f->error  = 0;

	if (mode == 'w')
	{
		f->available         = available - 8;
		f->next              = memory + 8;
		memory[0]            = 'V';
		memory[1]            = 'B';
		memory[2]            = 'A';
		memory[3]            = ' ';
		*((int *)(memory+4)) = 0;
	}
	else
	{
		if (memory[0] != 'V' || memory[1] != 'B' || memory[2] != 'A' ||
		    memory[3] != ' ')
		{
			free(f);
			return NULL;
		}
		f->available = *((int *)(memory+4));
		f->next      = memory+8;
	}

	return f;
}

local size_t memWrite(const void *buffer, size_t size, size_t count,
                      MEMFILE *file)
{
	size_t total = size*count;

	if (file->mode != 'w')
	{
		file->error = 1;
		return 0;
	}

	if (total > (size_t)file->available)
	{
		total = file->available;
	}
	memcpy(file->next, buffer, total);
	file->available -= (int)total;
	file->next      += total;
	return total;
}

local size_t memRead(void *buffer, size_t size, size_t count,
                     MEMFILE *file)
{
	size_t total = size*count;

	if (file->mode != 'r')
	{
		file->error = 1;
		return 0;
	}

	if (file->available == 0)
		return -1;

	if (total > (size_t)file->available)
	{
		total = file->available;
	}
	memcpy(buffer, file->next, total);
	file->available -= (int)total;
	file->next      += total;
	return total;
}

local int memPutc(int c, MEMFILE *file)
{
	if (file->mode != 'w')
	{
		file->error = 1;
		return -1;
	}

	if (file->available >= 1)
	{
		*file->next++ = c;
		file->available--;
	}
	else
		return -1;

	return c;
}

local long memTell(MEMFILE *f)
{
	return (long)(f->next - f->memory) - 8;
}

local int memError(MEMFILE *f)
{
	return f->error;
}

local int memClose(MEMFILE *f)
{
	if (f->mode == 'w')
	{
		*((int *)(f->memory+4)) = memTell(f);
	}
	free(f);
	return 0;
}

local int memPrintf(MEMFILE *f, const char *format, ...)
{
	char    buffer[80];
	va_list list;
	int     len;

	va_start(list, format);
	len = vsprintf(buffer, format, list);
	va_end(list);

	return (int)memWrite(buffer, 1, len, f);
}

/* ===========================================================================
     Opens a gzip (.gz) file for reading or writing. The mode parameter
   is as in fopen ("rb" or "wb"). The file is given either by file descriptor
   or path name (if fd == -1).
     gz_open return NULL if the file could not be opened or if there was
   insufficient memory to allocate the (de)compression state; errno
   can be checked to distinguish the two cases (if errno is zero, the
   zlib error is Z_MEM_ERROR).
 */
local gzFile gz_open(memory, available, mode)
char *memory;
const int   available;
const char *mode;
{
	int         err;
	int         level    = Z_DEFAULT_COMPRESSION; /* compression level */
	int         strategy = Z_DEFAULT_STRATEGY; /* compression strategy */
	char *      p        = (char *)mode;
	mem_stream *s;
	char        fmode[80]; /* copy of mode, without the compression level */
	char *      m = fmode;

	s = (mem_stream *)ALLOC(sizeof(mem_stream));
	if (!s)
		return Z_NULL;

	s->stream.zalloc   = (alloc_func)0;
	s->stream.zfree    = (free_func)0;
	s->stream.opaque   = (voidpf)0;
	s->stream.next_in  = s->inbuf = Z_NULL;
	s->stream.next_out = s->outbuf = Z_NULL;
	s->stream.avail_in = s->stream.avail_out = 0;
	s->z_err           = Z_OK;
	s->z_eof           = 0;
	s->crc             = crc32(0L, Z_NULL, 0);
	s->msg             = NULL;
	s->transparent     = 0;
	s->file            = NULL;

	s->mode = '\0';
	do
	{
		if (*p == 'r')
			s->mode = 'r';
		if (*p == 'w' || *p == 'a')
			s->mode = 'w';
		if (*p >= '0' && *p <= '9')
		{
			level = *p - '0';
		}
		else if (*p == 'f')
		{
			strategy = Z_FILTERED;
		}
		else if (*p == 'h')
		{
			strategy = Z_HUFFMAN_ONLY;
		}
		else
		{
			*m++ = *p; /* copy the mode */
		}
	}
	while (*p++ && m != fmode + sizeof(fmode));
	if (s->mode == '\0')
		return destroy(s), (gzFile)Z_NULL;

	if (s->mode == 'w')
	{
#ifdef NO_DEFLATE
		err = Z_STREAM_ERROR;
#else
		err = deflateInit2(&(s->stream), level,
		                   Z_DEFLATED, -MAX_WBITS, DEF_MEM_LEVEL, strategy);
		/* windowBits is passed < 0 to suppress zlib header */

		s->stream.next_out = s->outbuf = (Byte *)ALLOC(Z_BUFSIZE);
#endif
		if (err != Z_OK || s->outbuf == Z_NULL)
		{
			return destroy(s), (gzFile)Z_NULL;
		}
	}
	else
	{
		s->stream.next_in = s->inbuf = (Byte *)ALLOC(Z_BUFSIZE);

		err = inflateInit2(&(s->stream), -MAX_WBITS);
		/* windowBits is passed < 0 to tell that there is no zlib header.
		 * Note that in this case inflate *requires* an extra "dummy" byte
		 * after the compressed stream in order to complete decompression and
		 * return Z_STREAM_END. Here the gzip CRC32 ensures that 4 bytes are
		 * present after the compressed stream.
		 */
		if (err != Z_OK || s->inbuf == Z_NULL)
		{
			return destroy(s), (gzFile)Z_NULL;
		}
	}
	s->stream.avail_out = Z_BUFSIZE;

	errno   = 0;
	s->file = memOpen(memory, available, s->mode);

	if (s->file == NULL)
	{
		return destroy(s), (gzFile)Z_NULL;
	}

	if (s->mode == 'w')
	{
		/* Write a very simple .gz header:
		 */
		memPrintf(s->file, "%c%c%c%c%c%c%c%c%c%c", gz_magic[0], gz_magic[1],
		          Z_DEFLATED, 0 /*flags*/, 0, 0, 0, 0 /*time*/, 0 /*xflags*/, OS_CODE);
		s->startpos = 10L;
		/* We use 10L instead of ftell(s->file) to because ftell causes an
		 * fflush on some systems. This version of the library doesn't use
		 * startpos anyway in write mode, so this initialization is not
		 * necessary.
		 */
	}
	else
	{
		check_header(s); /* skip the .gz header */
		s->startpos = (memTell(s->file) - s->stream.avail_in);
	}

	return (gzFile)s;
}

/* ===========================================================================
     Opens a gzip (.gz) file for reading or writing.
 */
gzFile ZEXPORT memgzopen(memory, available, mode)
char *memory;
int         available;
const char *mode;
{
	return gz_open(memory, available, mode);
}

/* ===========================================================================
     Read a byte from a mem_stream; update next_in and avail_in. Return EOF
   for end of file.
   IN assertion: the stream s has been sucessfully opened for reading.
 */
local int get_byte(s)
mem_stream *s;
{
	if (s->z_eof)
		return EOF;
	if (s->stream.avail_in == 0)
	{
		errno = 0;
		s->stream.avail_in = (uInt)memRead(s->inbuf, 1, Z_BUFSIZE, s->file);
		if (s->stream.avail_in == 0)
		{
			s->z_eof = 1;
			if (memError(s->file))
				s->z_err = Z_ERRNO;
			return EOF;
		}
		s->stream.next_in = s->inbuf;
	}
	s->stream.avail_in--;
	return *(s->stream.next_in)++;
}

/* ===========================================================================
      Check the gzip header of a mem_stream opened for reading. Set the stream
    mode to transparent if the gzip magic header is not present; set s->err
    to Z_DATA_ERROR if the magic header is present but the rest of the header
    is incorrect.
    IN assertion: the stream s has already been created sucessfully;
       s->stream.avail_in is zero for the first time, but may be non-zero
       for concatenated .gz files.
 */
local void check_header(s)
mem_stream *s;
{
	int  method; /* method byte */
	int  flags; /* flags byte */
	uInt len;
	int  c;

	/* Check the gzip magic header */
	for (len = 0; len < 2; len++)
	{
		c = get_byte(s);
		if (c != gz_magic[len])
		{
			if (len != 0)
				s->stream.avail_in++, s->stream.next_in--;
			if (c != EOF)
			{
				s->stream.avail_in++, s->stream.next_in--;
				s->transparent = 1;
			}
			s->z_err = s->stream.avail_in != 0 ? Z_OK : Z_STREAM_END;
			return;
		}
	}
	method = get_byte(s);
	flags  = get_byte(s);
	if (method != Z_DEFLATED || (flags & RESERVED) != 0)
	{
		s->z_err = Z_DATA_ERROR;
		return;
	}

	/* Discard time, xflags and OS code: */
	for (len = 0; len < 6; len++)
		(void)get_byte(s);

	if ((flags & EXTRA_FIELD) != 0)   /* skip the extra field */
	{
		len  =  (uInt)get_byte(s);
		len += ((uInt)get_byte(s))<<8;
		/* len is garbage if EOF but the loop below will quit anyway */
		while (len-- != 0 && get_byte(s) != EOF)
			;
	}
	if ((flags & ORIG_NAME) != 0)   /* skip the original file name */
	{
		while ((c = get_byte(s)) != 0 && c != EOF)
			;
	}
	if ((flags & COMMENT) != 0)     /* skip the .gz file comment */
	{
		while ((c = get_byte(s)) != 0 && c != EOF)
			;
	}
	if ((flags & HEAD_CRC) != 0)    /* skip the header crc */
	{
		for (len = 0; len < 2; len++)
			(void)get_byte(s);
	}
	s->z_err = s->z_eof ? Z_DATA_ERROR : Z_OK;
}

/* ===========================================================================
 * Cleanup then free the given mem_stream. Return a zlib error code.
   Try freeing in the reverse order of allocations.
 */
local int destroy(s)
mem_stream *s;
{
	int err = Z_OK;

	if (!s)
		return Z_STREAM_ERROR;

	TRYFREE(s->msg);

	if (s->stream.state != NULL)
	{
		if (s->mode == 'w')
		{
#ifdef NO_DEFLATE
			err = Z_STREAM_ERROR;
#else
			err = deflateEnd(&(s->stream));
#endif
		}
		else if (s->mode == 'r')
		{
			err = inflateEnd(&(s->stream));
		}
	}
	if (s->file != NULL && memClose(s->file))
	{
#ifdef ESPIPE
		if (errno != ESPIPE) /* fclose is broken for pipes in HP/UX */
#endif
		err = Z_ERRNO;
	}
	if (s->z_err < 0)
		err = s->z_err;

	TRYFREE(s->inbuf);
	TRYFREE(s->outbuf);
	TRYFREE(s);
	return err;
}

/* ===========================================================================
     Reads the given number of uncompressed bytes from the compressed file.
   gzread returns the number of bytes actually read (0 for end of file).
 */
int ZEXPORT memgzread(file, buf, len)
gzFile file;
voidp    buf;
unsigned len;
{
	mem_stream *s     = (mem_stream *)file;
	Bytef *     start = (Bytef *)buf; /* starting point for crc computation */
	Byte *      next_out; /* == stream.next_out but not forced far (for MSDOS) */

	if (s == NULL || s->mode != 'r')
		return Z_STREAM_ERROR;

	if (s->z_err == Z_DATA_ERROR || s->z_err == Z_ERRNO)
		return -1;
	if (s->z_err == Z_STREAM_END)
		return 0;                            /* EOF */

	next_out = (Byte *)buf;
	s->stream.next_out  = (Bytef *)buf;
	s->stream.avail_out = len;

	while (s->stream.avail_out != 0)
	{
		if (s->transparent)
		{
			/* Copy first the lookahead bytes: */
			uInt n = s->stream.avail_in;
			if (n > s->stream.avail_out)
				n = s->stream.avail_out;
			if (n > 0)
			{
				zmemcpy(s->stream.next_out, s->stream.next_in, n);
				next_out += n;
				s->stream.next_out   = next_out;
				s->stream.next_in   += n;
				s->stream.avail_out -= n;
				s->stream.avail_in  -= n;
			}
			if (s->stream.avail_out > 0)
			{
				s->stream.avail_out -= (uInt)memRead(next_out, 1, s->stream.avail_out, s->file);
			}
			len -= s->stream.avail_out;
			s->stream.total_in  += (uLong)len;
			s->stream.total_out += (uLong)len;
			if (len == 0)
				s->z_eof = 1;
			return (int)len;
		}
		if (s->stream.avail_in == 0 && !s->z_eof)
		{
			errno = 0;
			s->stream.avail_in = (uInt)memRead(s->inbuf, 1, Z_BUFSIZE, s->file);
			if (s->stream.avail_in == 0)
			{
				s->z_eof = 1;
				if (memError(s->file))
				{
					s->z_err = Z_ERRNO;
					break;
				}
			}
			s->stream.next_in = s->inbuf;
		}
		s->z_err = inflate(&(s->stream), Z_NO_FLUSH);

		if (s->z_err == Z_STREAM_END)
		{
			/* Check CRC and original size */
			s->crc = crc32(s->crc, start, (uInt)(s->stream.next_out - start));
			start  = s->stream.next_out;

			if (getLong(s) != s->crc)
			{
				s->z_err = Z_DATA_ERROR;
			}
			else
			{
				(void)getLong(s);
				/* The uncompressed length returned by above getlong() may
				 * be different from s->stream.total_out) in case of
				 * concatenated .gz files. Check for such files:
				 */
				check_header(s);
				if (s->z_err == Z_OK)
				{
					uLong total_in  = s->stream.total_in;
					uLong total_out = s->stream.total_out;

					inflateReset(&(s->stream));
					s->stream.total_in  = total_in;
					s->stream.total_out = total_out;
					s->crc = crc32(0L, Z_NULL, 0);
				}
			}
		}
		if (s->z_err != Z_OK || s->z_eof)
			break;
	}
	s->crc = crc32(s->crc, start, (uInt)(s->stream.next_out - start));

	return (int)(len - s->stream.avail_out);
}

#ifndef NO_DEFLATE
/* ===========================================================================
     Writes the given number of uncompressed bytes into the compressed file.
   gzwrite returns the number of bytes actually written (0 in case of error).
 */
int ZEXPORT memgzwrite(file, buf, len)
gzFile file;
const voidp buf;
unsigned    len;
{
	mem_stream *s = (mem_stream *)file;

	if (s == NULL || s->mode != 'w')
		return Z_STREAM_ERROR;

	s->stream.next_in  = (Bytef *)buf;
	s->stream.avail_in = len;

	while (s->stream.avail_in != 0)
	{
		if (s->stream.avail_out == 0)
		{
			s->stream.next_out = s->outbuf;
			if (memWrite(s->outbuf, 1, Z_BUFSIZE, s->file) != Z_BUFSIZE)
			{
				s->z_err = Z_ERRNO;
				break;
			}
			s->stream.avail_out = Z_BUFSIZE;
		}
		s->z_err = deflate(&(s->stream), Z_NO_FLUSH);
		if (s->z_err != Z_OK)
			break;
	}
	s->crc = crc32(s->crc, (const Bytef *)buf, len);

	return (int)(len - s->stream.avail_in);
}
#endif
/* ===========================================================================
     Flushes all pending output into the compressed file. The parameter
   flush is as in the deflate() function.
 */
local int do_flush(file, flush)
gzFile file;
int flush;
{
	uInt        len;
	int         done = 0;
	mem_stream *s    = (mem_stream *)file;

	if (s == NULL || s->mode != 'w')
		return Z_STREAM_ERROR;

	s->stream.avail_in = 0; /* should be zero already anyway */

	for (;;)
	{
		len = Z_BUFSIZE - s->stream.avail_out;

		if (len != 0)
		{
			if ((uInt)memWrite(s->outbuf, 1, len, s->file) != len)
			{
				s->z_err = Z_ERRNO;
				return Z_ERRNO;
			}
			s->stream.next_out  = s->outbuf;
			s->stream.avail_out = Z_BUFSIZE;
		}
		if (done)
			break;
		s->z_err = deflate(&(s->stream), flush);

		/* Ignore the second of two consecutive flushes: */
		if (len == 0 && s->z_err == Z_BUF_ERROR)
			s->z_err = Z_OK;

		/* deflate has finished flushing only when it hasn't used up
		 * all the available space in the output buffer:
		 */
		done = (s->stream.avail_out != 0 || s->z_err == Z_STREAM_END);

		if (s->z_err != Z_OK && s->z_err != Z_STREAM_END)
			break;
	}
	return s->z_err == Z_STREAM_END ? Z_OK : s->z_err;
}

/* ===========================================================================
   Outputs a long in LSB order to the given file
 */
local void putLong(file, x)
MEMFILE *file;
uLong x;
{
	int n;
	for (n = 0; n < 4; n++)
	{
		memPutc((int)(x & 0xff), file);
		x >>= 8;
	}
}

/* ===========================================================================
   Reads a long in LSB order from the given mem_stream. Sets z_err in case
   of error.
 */
local uLong getLong(s)
mem_stream *s;
{
	uLong x = (uLong)get_byte(s);
	int   c;

	x += ((uLong)get_byte(s))<<8;
	x += ((uLong)get_byte(s))<<16;
	c  = get_byte(s);
	if (c == EOF)
		s->z_err = Z_DATA_ERROR;
	x += ((uLong)c)<<24;
	return x;
}

/* ===========================================================================
     Flushes all pending output if necessary, closes the compressed file
   and deallocates all the (de)compression state.
 */
int ZEXPORT memgzclose(file)
gzFile file;
{
	int         err;
	mem_stream *s = (mem_stream *)file;

	if (s == NULL)
		return Z_STREAM_ERROR;

	if (s->mode == 'w')
	{
#ifdef NO_DEFLATE
		return Z_STREAM_ERROR;
#else
		err = do_flush(file, Z_FINISH);
		if (err != Z_OK)
			return destroy((mem_stream *)file);

		putLong(s->file, s->crc);
		putLong(s->file, s->stream.total_in);
#endif
	}
	return destroy((mem_stream *)file);
}

long ZEXPORT memtell(file)
gzFile file;
{
	mem_stream *s = (mem_stream *)file;

	if (s == NULL)
		return Z_STREAM_ERROR;

	return memTell(s->file);
}
